Wave guide bend



Jan. 20, 1948. A. G. FOX 34,645

WAVE GUIDE BEND Original Filed June 50, 1942 //V 5 N TOR AG. FO BY ATTORNEY Patented Jan. 20, 1948 WAVE GUIDE BEND Arthur Gardner Fox, Red Bank, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application July 30, 1942, Serial No. 452,851. Divided and this application August 17, 1945, Serial No. 610,957

3 Claims. (01. 178-44) This invention relates to guided electromagnetic wave transmission and more particularly to bends for wave guides.

The object of the invention is to connect; without appreciable reflection two wave guides which are joined at an angle of less than 180 degrees.

A further object is to connect without appreciable reflection two such wave guides which differ in characteristic impedance.

In accordance with the invention, two wave guides which meet at an angle of less than 180 degrees are joined with substantially no reflection. The guides may differ in characteristic impedance, in which case the bend has the further property of impedance transformation. The one guide extends beyond the junction and has therein a transverse reflecting plate positioned for optimum transmission of energy past the junction. This plate is located at a distance from the mid-point of the junction approximately equal to a half wavelength for bends in the electric plane and approximately equal to a quarter wavelength for bends in the magnetic plane. The other guide communicates at its end with the one guide through an aperture of smaller area than the cross-sectional area of the other guide, and this aperture is adjusted to the proper size for substantially refiectionless transmission of energy.

past the junction.

This is a division of United States patent application Serial No. 452,851, filed July 30, 1942, now Patent No. 2,432,093.

The nature of the invention will be more fully understood from the following detailed description and by reference to the accompanying drawing the single figure of which is a perspective view, partly cut away, of an impedance transforming bend for a wave guide in accordance with the invention.

The figure shows how two hollow wave guides 42 and 43 of unequal characteristic impedance may be connected together in a right angle substantially without reflection. The guide 43 which has the lower characteristic impedance extends beyond the junction and is closed by a slidable reflecting plate 44 which may be moved by means of the push rod 46. The plate 44 is located at a distance from the mid-point of the junction which, for bends in the electric Plane, is equal approximately to a half wavelength within the guide 43 and, for bends in the magnetic plane, is equal approximately to a quarter wavelength. The proper location of the plate 44 is the one which gives optimum transmission and may be found by trial. There will, however, generally be reflections of energy due to a mismatch of impedances at the junction of the two guides. These reflections may be substantially eliminated by adding a metallic flap 45 by means of which the opening D of the junction aperture may be adl'usted to the proper size.

What is claimed is:

1. In combination, two hollow wave guides of rectangular cross-section joined together to form an approximately right angle bend in the electric plane of the guided waves, said guides differing in characteristic impedance, the longer cross-sectional dimensions of said guides being equal, one of said guides including therein a transverse reflecting plate located at a distance beyond the junction equal approximately to a half wavelength at the mid-band frequency to be transmitted, the other of said guides having at its end an opening into said one guide, said opening having an area which is the same as the cross-sectional area of said other guide except for a partially obstructing flap which is substantially an extension of one of the wider sides of said one guide, and the area of said opening being so chosen as to provide substantially reflectionless transmission of energy past said junction.

2. The combination in accordance with claim 1 in which said one guide has the lower characteristic impedance.

3. The combination in accordance with claim 1 in which said reflecting plate is movable longitudinally along said one guide.

ARTHUR GARDNER FOX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,151,118 King Mar. 21. 1939 2,206,923 Southworth July 9, 1940 

